JP2009097053A - Metal strip, connector, and mehod of manufacturing metal strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal strip necessary to a lead-free connector, good in solderability to a substrate, generating no whisker at terminal part when storing it and fitting it to FPC (flexible printed circuit board) or FFC (flexible flat cable). <P>SOLUTION: An Ni plating is applied to the base metal of the metal strip, then a Sn-(1-4 mass%)Cu plating containing no brightener is applied onto it. By heat-treating this metal strip at a temperature of melting point (solid phase line) of a Cu alloy or higher, a Cu-Sn compound layer or a Cu-Ni-Sn compound layer is formed on the Ni-plated layer, and also an Sn layer or an Sn-Cu alloy layer is formed on the Cu-Sn compound layer or the Cu-Ni-Sn compound layer. Furthermore, this metal strip is worked to form connectors. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a terminal constituting an electrical connector, in particular a connector terminal mated for electrical connection with another member such as FPC (flexible printed circuit board), FFC (flexible flat cable), etc., and The present invention relates to a metal strip constituting this and a manufacturing method thereof. In particular, the present invention relates to a lead-free plated connector terminal having a narrow pitch that has been subjected to lead-free plating, and a metal strip constituting the terminal.

  Since the terminals constituting the connector are soldered when attached to the substrate, the entire surface of the metal strip constituting the terminals is generally plated. For low environmental impact lead-free plating, from the viewpoint of solderability, contact reliability, and corrosion resistance, a Sn-based solder layer is formed on the Ni underlayer, or Sn plating is applied to Cu or Cu alloys. Inexpensive Sn plating materials that have been applied are known. Further, in the case of a narrow pitch connector having a pitch of 0.5 mm or less, it is necessary to simultaneously suppress the growth of whiskers that may come into contact with the adjacent connector terminal and cause a short circuit.

  There has been proposed a method for securing solderability and corrosion resistance by applying Ni plating on a base metal and applying Sn-Cu plating thereon (Patent Document 1). In addition, a method has been proposed in which whisker is prevented from being generated from a contact portion at the time of connection by performing Ni or Cu base plating on a base metal and then Sn-Bi plating thereon (Patent Document). 2). Furthermore, by forming a plating layer having a Ni layer, a Ni-Sn intermetallic compound layer, a Ni-Sn intermetallic compound and Sn mixed layer, and an oxidized Sn layer in order on the base metal, whisker generation can be prevented. A method for achieving both solder wettability has also been proposed (Patent Document 3). Moreover, Ni or Ni alloy layer is sequentially applied from the Cu or Cu alloy side by applying Ni or Ni alloy plating, Cu plating, Sn or Sn alloy plating on the surface of Cu or Cu alloy, and performing heat treatment at 400 to 900 ° C. A method that provides good solderability, whisker resistance, heat resistance reliability, and molding processability by forming a layer composed mainly of Cu and Sn or Cu and Sn and Ni, and an Sn or Sn alloy layer in this order. It has been proposed (Patent Document 4).

JP 2002-164106 A JP 2005-56605 A JP 2006-49083 A JP 2003-293187 A

  However, as in Patent Document 1, the metal strip provided by simply Sn-Cu plating on the Ni base plating ensures solder wettability and corrosion resistance, but it is difficult to suppress whisker growth. is there. Cu-Sn compounds are not formed at the interface between the Ni base plating and Sn-Cu plating by simply performing two-layer plating, and Ni will selectively diffuse Sn grain boundaries during Sn-Cu plating when stored for a long period of time. As a result, the Ni-Sn compound grows along the Sn grain boundary, and an internal compression pressure is generated due to the local volume change accompanying this, which destroys the outermost Sn oxide film and generates and grows whiskers. End up.

  Further, as in Patent Document 2, it is difficult to completely suppress whisker generation by simply performing Sn—Bi plating on the Ni or Cu base plating of the metal strip. Ni or Cu reacts with Sn-Bi plating Sn during reflow, Ni-Sn compound or Cu-Sn compound is formed at the interface, and there is no reaction barrier layer. . As a result, a large internal compressive stress is generated inside the plating, and as a result, whisker is generated although the frequency of occurrence is lower than that of the Ni base plating / Sn—Cu plating.

  Furthermore, as in Patent Document 3, in the method of forming a plating layer having a Ni layer, a Ni—Sn intermetallic compound layer, a mixed layer composed of a Ni—Sn intermetallic compound and Sn, and an oxidized Sn layer in this order, Ni— The Sn compound grows as much as it reaches the Sn oxide layer on the surface, and a large amount of Ni-Sn compound is generated, so that a large internal compressive stress is generated inside the plating, which has the support column effect of the Ni-Sn compound. However, whiskers will occur. In addition, since a part of the Ni—Sn compound reaches the Sn oxide layer on the surface, the solder wettability is also inferior compared to the case where it is not.

  Further, in Patent Document 4, since the Cu—Sn compound layer is formed on the Ni layer by heat treatment, Ni and Sn—Cu plating layer are not in contact with each other, so that the growth of the Ni—Sn compound can be suppressed. As a result, whisker growth caused by internal compressive stress can be suppressed. However, as whisker countermeasures, only whiskers due to the internal compressive stress of the plating film are considered, and the plating film becomes very hard by heat treatment at a high temperature of 400 to 900 ° C., which occurs during connector mating. Whisker caused by external compressive stress cannot be suppressed.

  The present invention solves the above-mentioned problems, and suppresses whisker growth caused by internal compressive stress in the plating film (inhibition of growth of the intermetallic compound layer inside the plating film), and external compressive stress generated during connector mating. The present invention provides a connector terminal that suppresses the resulting whisker growth and ensures solder wettability, and a metal strip constituting the connector terminal.

  Here, a connector is mainly used as a usage form of the metal strip. FPC or FFC is generally used for flexible connection between the terminals of the board. In this case, it is necessary to solder the connectors to the terminals of both boards and connect both connectors via FPC or FFC. Of these connectors, in particular, the terminal pitch is a narrow pitch of 0.5 mm or less, The metal strip of the present invention can be used for a lead-free connector.

The following is a brief description of an outline of typical inventions disclosed in the present application.
(1) Base metal, Ni layer formed on the base metal, Cu-Sn compound layer or Cu-Ni-Sn compound layer formed on the Ni layer, Cu-Sn compound layer or And a Sn layer or an Sn—Cu alloy layer formed on the Cu—Ni—Sn compound layer, and having a Vickers hardness of 100 or less.
(2) The metal strip according to (1) 1, wherein the total Cu with respect to the total amount of Sn + Cu in the Sn layer or Sn-Cu alloy layer and the Cu-Sn compound layer or Cu-Ni-Sn compound layer The metal strip is characterized in that the proportion of the amount is 1 to 4 mass%.
(3) A method for producing a metal strip, comprising a step of sequentially laminating a Ni layer and a Sn- (1 to 4 mass%) Cu alloy layer on a base metal, and forming the stacked base metal into the Sn- ( 1 to 4 mass%) Heat treatment at a temperature equal to or higher than the solidus temperature of the Cu alloy, and a Cu-Sn compound layer or Cu-Ni-Sn compound layer, the Cu-Sn compound layer or Cu-Ni-Sn on the Ni layer Forming a Sn layer or a Sn—Cu alloy layer on the compound layer.
(4) The method for producing a metal strip according to (3), wherein the Sn- (1 to 4 mass%) Cu alloy layer is laminated by matte plating.

  According to the present invention, whisker growth caused by internal compressive stress in the plating film is suppressed (inhibition of growth of the intermetallic compound layer inside the plating film), and whisker growth caused by external compressive stress generated during connector mating is also suppressed. It is possible to provide a metal strip that secures solder wettability, and a connector formed thereby.

First, 1st Embodiment of the metal strip which concerns on this invention is described using FIG.
FIG. 1 shows a cross section of a layer structure of a metal strip 1 according to the present invention. On a base metal 2, a Ni layer 3 and a Cu—Sn compound layer or Cu formed on the Ni layer 3 are shown. A layered structure is provided which is formed on the Ni-Sn compound layer 4 and the Cu-Sn compound layer or the Cu-Ni-Sn compound layer 4 and includes a brightener-free Sn layer or Sn-Cu alloy layer 5. Yes. The metal strip 1 has a Vickers hardness of 100 or less.
In this structure, it is important that a double reaction barrier layer is formed between the base metal 2 and the Sn layer or Sn—Cu alloy layer 5 not containing the brightener. That is, according to this, the reaction between the Ni layer 3 and the Sn layer or Sn—Cu alloy layer 5 not containing the brightener can be suppressed by the Cu—Sn compound layer or the Cu—Ni—Sn compound layer 4, and The reaction between the base metal 2 and the Cu—Sn compound layer or Cu—Ni—Sn compound layer 4 and the Sn layer or Sn—Cu alloy layer 5 not containing the brightener can be suppressed by the Ni layer 3. Ni—Sn compound, Cu—Sn compound and Cu—Ni—Sn compound growth in the plating film can be prevented, and Sn whisker caused by internal compressive stress generated from the surface of the metal strip can be suppressed. In general, as the base metal 2, a Cu alloy such as phosphor bronze is often used, and the promotion of compounding by the Cu supply from this Cu alloy may cause whiskers. Since the Cu supply from the metal is interrupted and the reaction between the base metal and the Cu—Sn compound layer or the Cu—Ni—Sn compound layer 4 is suppressed, the metal strip having the layer structure of the present invention is used. Ordinary phosphor bronze can be used without using metal as a special material.

  Also, in this structure, Vickers hardness is set to 100 or less, so even when external pressure is applied by engaging with FPC or FFC, compressive stress is not generated in the engaged part. Also, whisker growth caused by external compressive stress can be suppressed.

The thickness of the Ni layer 3 of this structure is preferably in the range of 0.05 to 1.0 μm. When the thickness of the Ni layer 3 is less than 0.05 μm, the base metal 2 and the Cu—Sn compound layer or Cu—Ni—Sn compound layer 4 and the Sn layer or Sn—Cu alloy layer 5 not containing the brightener are included. This is because the function of inhibiting the reaction between the two does not sufficiently function, and if it is thicker than 1.0 μm, the moldability of the metal strip is deteriorated.
The Cu-Sn compound formed is mainly Cu ₆ Sn ₅ and the Cu-Ni-Sn compound formed is mainly (Cu, Ni) ₆ Sn _5, but Cu ₃ Sn and (Cu , Ni) ₃ Sn may be partially formed. Moreover, the Cu ratio in the Sn—Cu alloy layer 5 is usually 0.7 to 0.9 mass%, which is a Sn—Cu eutectic composition.
Furthermore, the total thickness of the surface layers (Ni layer 3, Cu-Sn compound layer or Cu-Ni-Sn compound layer 4, Sn layer or Sn-Cu alloy layer 5 not containing brightener) is in the range of 1 to 10 μm. It is preferable that This is because if the thickness is less than 1 μm, the solder wettability is lowered, and if it exceeds 10 μm, the moldability of the metal strip is deteriorated.

  Here, in this structure, the Ni layer is the first layer, the Cu-Sn compound layer or Cu-Ni-Sn compound layer is the second layer, and the Sn layer or Sn-Cu alloy layer not containing the brightener is the third layer. Although a metal strip having a Vickers hardness of 100 or less has been described as an example, the present invention is not limited to this, and it is not limited to this, and a material that can be configured to prevent the progress of compounding by forming a double reaction barrier layer. As long as it is a combination and the Vickers hardness is set to 100 or less, various modifications can be made without departing from the scope of the invention. For example, a Zn—Sn compound layer may be used as the second layer, and a layer having a eutectic composition of Sn and Zn having a Vickers hardness of 100 or less may be used as the third layer. Further, the first layer may be a Co layer, an Fe layer, or the like.

Next, the manufacturing method of the metal strip which concerns on this invention is demonstrated.
FIG. 2 is a cross-sectional view of the first laminated structure of the metal strip 6 before heat treatment used for manufacturing the metal strip according to the present invention. The Ni layer 3 is formed on the base metal 2 and the Ni layer 3 is not coated. The bright Sn—Cu alloy layer 7 is formed by sequentially providing plating or the like. Here, the matte Sn—Cu alloy layer 7 formed on the Ni layer 3 is used to form a Cu—Sn compound layer or a Cu—Ni—Sn compound layer 4 directly on the Ni layer 3 by a heat treatment described later. Necessary.
Note that the thickness of the matte Sn—Cu alloy layer 7 is preferably in the range of 1 to 5 μm. This is because if the thickness is less than 1 μm, the solder wettability decreases, and if it exceeds 5 μm, the moldability of the metal strip deteriorates. Further, the Sn—Cu alloy layer 7 may contain 1 mass% or less of one or more metals selected from Zn, Al, Si, Mg, and Ti. By containing a small amount of these oxidizable metals, these metals are selectively oxidized during the subsequent heat treatment and reflow, so that the oxidation of the outermost Sn-Cu alloy layer can be minimized. It is possible to suppress the generation of internal compressive stress in the plating film due to the lid effect of the outermost oxidized Sn layer and the generation of whiskers associated therewith.

  After the above layer forming treatment, the matte Sn—Cu alloy layer 7 is partially melted by heat-treating the metal strip 6 at a temperature equal to or higher than the solidus of the matte Sn—Cu alloy layer 7. As a result, a part of the Cu—Sn compound existing in a floating island shape in the matte Sn—Cu alloy layer 7 melts, and this is differentially deposited immediately above the Ni layer 3 to form a Cu—Sn compound layer. . Further, when the temperature is raised to a temperature higher than the liquidus, the matte Sn—Cu alloy layer 7 is completely melted. Thereafter, when cooled, the Cu—Sn compound is reprecipitated. At this time, Ni becomes the nucleus of reprecipitation, and the Cu—Sn compound is precipitated on the Ni layer 3. Here, when the heat treatment temperature is lower than the liquidus temperature, the Cu-Sn compound may end only by reprecipitation, but when the heat treatment temperature is higher than the liquidus temperature, the Cu-Sn compound may end. At the same time as it precipitates, it reacts with the Ni layer 3 to form a Cu—Sn compound layer or a Cu—Ni—Sn compound 4 immediately above the Ni layer 3.

After the heat treatment, the surface layer becomes the Sn layer or Sn—Cu alloy layer 5 containing no brightener. The Cu ratio in the Sn—Cu alloy layer not containing the brightener is usually 0.7 to 0.9 mass%, which is a Sn—Cu eutectic composition. In this case, since the surface layer has a relatively small amount of Sn oxide, it is possible to provide a metal strip having good solder wettability at the time of subsequent connection.
Here, a brightening agent is used for the matte Sn—Cu alloy layer 7 which is the basis of the Sn layer or Sn—Cu alloy layer 5 of the manufactured metal strip 1 and the Cu—Sn compound layer or Cu—Ni—Sn compound layer 4. Since the Vickers hardness of the metal strip 1 is as low as 100 or less even after the heat treatment for obtaining the metal strip 1 is not included, the external generated when mating with FPC, FCC, etc. Whisker caused by compressive stress can be suppressed.
The surface layer is usually the most stable Sn—Cu alloy layer (Sn—Cu eutectic composition), but when the surface layer becomes extremely thin, for example, about 2 μm or less, the surface layer May be Sn. When the layer thickness is 2 μm or less, the Cu-Sn compound layer or Cu-Ni-Sn compound side where all the Cu components are under the surface layer rather than existing as a layer of Sn-Cu eutectic composition This is because it becomes more stable when the surface layer is an Sn layer.

  Here, the heat treatment is desirably performed at 350 ° C. or lower. When heat treatment is performed at a temperature of 350 ° C or higher, the Vickers hardness becomes higher than 100, and compressive stress is generated in the mating part when it is mated with FPC or FFC and external stress is applied. In addition to the occurrence and growth of whiskers, the degree of surface oxidation increases, and the solder wettability deteriorates significantly.

  In order to set the heat treatment temperature to 350 ° C. or less, the ratio of Cu in the matte Sn—Cu alloy layer 7 needs to be 4 mass% or less. Moreover, if the ratio of Cu in the matte Sn—Cu alloy layer 7 is less than 1 mass%, the difference from the Cu ratio of 0.7 to 0.9 mass% in the Sn—Cu alloy eutectic is too small, so The amount of the deposited Cu-Sn compound or Cu-Ni-Sn compound is too small, and a Cu-Sn compound or Cu-Ni-Sn compound is formed on a part of the Cu-Sn compound layer or Cu-Ni-Sn compound layer 4 A portion not formed is formed, and the reaction between the Ni layer 3 and the Sn layer or Sn—Cu alloy layer 5 not containing the brightener cannot be completely prevented. Therefore, the ratio of Cu in the matte Sn—Cu alloy layer 7 needs to be 1 to 4 mass%. In addition, in the case of Sn- (1-4 mass%) Cu composition, solidus temperature is 227 degreeC and liquidus temperature is about 235-350 degreeC.

  That is, by setting the Cu ratio of the matte Sn—Cu alloy layer 7 on the Ni layer 3 to 1 to 4 mass% and performing heat treatment at a temperature of 350 ° C. or less, the Vickers hardness of the metal strip 1 becomes 100 or less, and the internal It is possible to achieve both whisker suppression due to stress and whisker suppression due to external stress.

  In general, matte plating used as described above is known to have significantly poorer solder wettability compared to bright plating, but it can be improved to a practical level by heat treatment at a low temperature of 350 ° C or lower. it can.

In the above description, the laminated structure of the Ni layer 3 and the matte Sn-Cu alloy layer 7 is described as an example of the pre-heat treatment metal strip 6 used for manufacturing the metal strip of the present invention. As shown in FIG. 3, the second laminated structure may be formed by sequentially laminating a Ni layer 3, a Cu layer 8, and a Sn layer 9 not using a brightener on the base metal 2. . The Sn layer 9 may contain 1 mass% or less of one or more metals selected from Zn, Al, Si, Mg, and Ti. By containing a small amount of these oxidizable metals, these metals are selectively oxidized at the time of subsequent heat treatment or reflow, so that the oxidation of the outermost Sn layer 7 can be minimized. In addition, it is possible to suppress the generation of internal compressive stress in the plating film due to the lid effect of the outermost Sn oxide layer and the generation of whiskers associated therewith.
In this case, after the layer formation treatment, the metal strip is heat-treated at a temperature not lower than the melting point of Sn and at least not lower than the solidus of the Sn—Cu alloy and not higher than 350 ° C. Since the Cu-Sn compound layer or Cu-Ni-Sn compound layer is formed immediately above the Ni layer 3 and the Sn layer or Sn-Cu alloy layer is formed on the surface layer, the Vickers hardness is 100 or less. The metal strip 1 having an effect can be manufactured.

  The results of specific experiments are shown below.

Regarding the metal strip samples of the present invention (Examples 1 to 9) and the conventional metal strip samples (Comparative Examples 1 to 4), the occurrence of Vickers hardness and whisker (caused by internal stress and external stress) was examined. The results are shown in FIG. For the sample, a phosphor bronze base metal (32 mm x 15 mm x 0.25 mm thickness) was used. After the electrolytic degreasing treatment and acid activation treatment were performed as pre-plating treatment, a plating layer was applied to the surface. It formed one by one by the plating method. A fluorescent X-ray film thickness meter was used to measure the plating film thickness. Thereafter, heat treatment was carried out by holding at a predetermined temperature for 10 seconds in N2.
The Vickers hardness of the metal strip sample surface was measured using a micro Vickers hardness meter at a creep rate of 5 gf / 2 s and a creep time of 5 s.

The confirmation of whisker generation was performed as follows. FPC was fitted into a connector formed by processing a metal strip sample, and after standing for 1000 hours at room temperature and 50% relative humidity, observation was performed with a metal microscope and a scanning electron microscope. The whisker length is the maximum length.
In Examples 1 to 9, the Vickers hardness was relatively soft at 100 or less, whisker generation due to internal stress was not observed, and the whisker due to external stress was 20 μm or less in maximum length.

FIG. 5 shows the results of examining the solder wettability of the metal strip samples of the present invention (Examples 1 to 9) and the conventional metal strip samples (Comparative Examples 1 to 4).
The evaluation of solder wettability was performed by measuring the zero crossing time and the maximum wettability using a meniscograph. As a test sample, a metal strip of 15 mm × 3 mm × thickness 0.25 mm was used. Sn-3Ag-0.5Cu was used for the bath solder, and the bath temperature was 240 ° C. The descending speed was 2.0 mm / s, the immersion depth was 2.0 mm, and the holding time was 20 s. Before the sample was immersed in the solder bath, the tip was immersed in 25 mass% WW Rosin / IPA flux for about 3 mm for 5 seconds to apply the flux.

In Examples 1 to 9, the zero crossing time was relatively short, the maximum wetting force was relatively large, and good solder wettability was obtained.
In Comparative Examples 1 to 4 using conventional metal strip samples, there was a problem with either whisker generation (caused by internal stress or external stress) or solder wettability.
Among the examples and comparative examples, the Cu—Ni—Sn compound layer was heat-treated at a temperature lower than the liquidus temperature immediately above the Ni layer of the sample heat-treated at a temperature higher than the liquidus temperature of the Sn—Cu alloy layer. A Cu—Sn compound layer was formed immediately above the Ni layer of the sample. Further, in the sample of Example 9 having a thin Sn—Cu plating thickness of 1.5 μm, after the heat treatment, the outermost surface layer did not become the Sn—0.75Cu layer but became the Sn layer.

  From the above experimental results, it was found that the metal strip according to the present invention is good in both whisker resistance (inhibition of internal stress-induced whisker and external stress-induced whisker) and solder wettability.

It is typical sectional drawing of the layer structure of the metal strip which concerns on this invention. It is typical sectional drawing of the 1st layer structure of the metal strip before heat processing used in order to manufacture the metal strip which concerns on this invention. It is typical sectional drawing of the 2nd layer structure of the metal strip before heat processing used in order to manufacture the metal strip which concerns on this invention. It is a figure which shows the whisker generation | occurrence | production situation of the metal strip of this invention and the conventional metal strip. It is a figure which shows the solder wettability of the metal strip of this invention, and the conventional metal strip.

Explanation of symbols

1 Metal strip 2 Base metal 3 Ni layer 4 Cu-Sn compound layer or Cu-Ni-Sn compound layer 5 Sn layer or Sn-Cu alloy layer containing no brightener 6 Metal strip before heat treatment 7 Matte Sn-Cu Alloy layer 8 Cu layer 9 Sn layer

Claims (12)

With base metal,
Ni layer formed on the base metal,
Cu-Sn compound layer or Cu-Ni-Sn compound layer formed on the Ni layer, and Sn layer or Sn-Cu alloy layer formed on the Cu-Sn compound layer or Cu-Ni-Sn compound layer And a metal strip characterized by having a Vickers hardness of 100 or less. The metal strip according to claim 1,
The ratio of the total Cu amount to the total total amount of Sn + Cu in the Sn layer or Sn-Cu alloy layer and the Cu-Sn compound layer or Cu-Ni-Sn compound layer is 1 to 4 mass%, Metal strip. The metal strip according to claim 1 or 2,
The metal layer, wherein the Sn layer or the Sn—Cu alloy layer is an outermost surface layer and is a matte layer. The metal strip according to any one of claims 1 to 3,
The Ni layer and the Sn layer or the Sn—Cu alloy layer are not in contact with each other by the Cu—Sn compound layer or the Cu—Ni—Sn compound layer formed therebetween. . The metal strip according to any one of claims 1 to 4,
The Cu-Sn compound layer or the Cu-Ni-Sn compound layer is formed in contact with the Ni layer, and the Sn layer or the Sn-Cu alloy layer does not contact the Ni layer, A metal strip characterized by being formed in contact with the Cu-Sn compound layer or the Cu-Ni-Sn compound layer. A metal strip according to any one of claims 1 to 5,
The Sn layer or the Sn-Cu alloy layer and the Cu-Sn compound layer or the Cu-Ni-Sn compound layer heat-treat the Sn-Cu alloy plating layer that does not contain a brightener laminated on the Ni layer. Metal strip characterized by being formed. The metal strip according to any one of claims 1 to 6,
The metal strip is characterized in that the base metal is a Cu alloy. The metal strip according to claim 7,
The metal strip is characterized in that the base metal is phosphor bronze. A connector formed by processing the metal strip according to any one of claims 1 to 8. A method of manufacturing a metal strip,
A step of sequentially laminating a Ni layer and a Sn- (1-4 mass%) Cu alloy layer on the base metal;
The laminated base metal is heat-treated at a temperature equal to or higher than the solidus temperature of the Sn- (1 to 4 mass%) Cu alloy, and a Cu-Sn compound layer or a Cu-Ni-Sn compound layer on the Ni layer, Forming a Sn layer or a Sn-Cu alloy layer on the Cu-Sn compound layer or Cu-Ni-Sn compound layer. It is a manufacturing method of the metal strip according to claim 10,
The Sn- (1-4 mass%) Cu alloy layer is laminated by matte plating, and the method for producing a metal strip. It is a manufacturing method of the metal strip according to claim 10 or 11,
The Sn- (1-4 mass%) Cu alloy layer contains 1 mass% or less of at least one metal selected from Zn, Al, Si, Mg, and Ti.

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